Title: Grafting of cellulose, microcrystalline cellulose via polycondensation with oligo(lactic acid) and its applications in poly(L-lactic acid) based composites preparation

Abstract

Poly(L-lactic acid) (PLLA) is a biodegradable polyester derived from renewable resources and used for both medical and ecological purposes. However, PLLA is not utilized in some applications due to further requirements for high impact strength and thermal stability. Properties of PLLA can be enhanced by blending or composite preparation with α-cellulose andmicro-crystalline cellulose (MCC). To increase the compatibility, oligo(L lactic acid) (OLLA) grafted onto their surfaces by graft poly-condensation reaction in toluene at 1300C under 380 mmHg. Para-toluene sulphonic acid (5 wt.%) and potassium persulfate (0.01 wt.%) were acted as catalyst and co-catalyst in this reaction. For OLLA synthesis, ring-opening polymerization of L-lactides were carried out in the presence of stannous octoate (0.03 wt.%) as the initiator with L-lactic acids as the co-initiator; at 1400C. Grafting was observed by FTIR and SEM analysis. FTIR absorption at 1730.15 cm-1 may due to bond formation between hydroxyl groups of α-cellulose and OLLA and spotted area of SEM images confirmed grafting of OLLA onto α-cellulose and MCC surface. MCC shows better grafting than that of α-cellulose. The surface morphology and thermal properties of the composites were investigated by SEM, XRD and thermal analysis (TGA, DTA, and DTG). SEM images of composite shows homogeneous distribution of grafted α-cellulose and MCC. WAXD profiles indicate only homo crystallization occurs in the composites. The results show an adequate compatibility between grafted α-cellulose/MCC and PLLA. Maximum weight loss temperature, degradation temperature and melting temperature of the composites increases with increasing grafted α-cellulose/ MCC up to 15%. TGA and DTA results are indicating that grafted α-cellulose/MCC can improve thermal properties of PLLA based composites. DTG analysis also supports TGA and DTA results. This composite may have biomedical (scaffold, wound dressing) and ecological (food packaging, one time cup, plate, glass) applications.